Recent home networks establish co-operations among audio-visual home appliances through the Internet Protocol (IP) connection in wireless networks including Ethernet (Registered) and a wireless local area network (LAN). In addition, these networks are acquiring functions for co-operating equipment items—the functions to let various equipment items connect with the networks—through a home energy management system (HEMS). The HEMS is capable of managing electricity consumption in view of environment issues and managing power source for equipment items (including home appliances) through remote control outside a building.
Some of the home network systems allow a co-operation between a mobile terminal, such as a smart phone, and indoor equipment items. Hence, in the future, these systems may allow a user to lock and unlock his or her house doors with, for example, his or her mobile terminal. The user, however, takes the mobile terminal with him or her. Hence, out of the house, the user could have such problems as misplacing the mobile terminal or having the mobile terminal stolen. Consequently, an assumed case is that a malicious third party uses the stolen mobile terminal to intrude the user's house.
As a counter-measure against such a case, the user could create a password when turning on and off the mobile terminal and activating an application to lock and unlock a house door. The measure, however, is very troublesome and inconvenient for a user who uses the mobile terminal every day. One of exemplary techniques to solve such a problem is disclosed in Patent Literature 1.